Rotation and interaction of the September 8 and 10, 2014 CMEs tested with EUHFORIA. (arXiv:2305.06881v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Maharana_A/0/1/0/all/0/1">Anwesha Maharana</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Scolini_C/0/1/0/all/0/1">Camilla Scolini</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schmieder_B/0/1/0/all/0/1">Brigitte Schmieder</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Poedts_S/0/1/0/all/0/1">Stefaan Poedts</a>
Solar coronal mass ejections (CMEs) can catch up and interact with preceding
CMEs and solar wind structures to undergo rotation and deflection during their
propagation. We aim to show how interactions undergone by a CME in the corona
and heliosphere can play a significant role in altering its geoeffectiveness
predicted at the time of its eruption. We consider a case study of two
successive CMEs launched from the active region NOAA 12158 in early September
2014. The second CME was predicted to be extensively geoeffective based on the
remote-sensing observations of the source region. However, in situ measurements
at 1~au recorded only a short-lasting weak negative Bz component followed by a
prolonged positive Bz component. The EUropean Heliosphere FORecasting
Information Asset (EUHFORIA) is used to perform a self-consistent 3D MHD
simulation of the two CMEs in the heliosphere. The initial conditions of the
CMEs are determined by combining observational insights near the Sun,
fine-tuned to match the in situ observations near 1~au, and additional
numerical experiments of each individual CME. By introducing CME1 before CME2
in the EUHFORIA simulation, we modelled the negative Bz component in the sheath
region ahead of CME2 whose formation can be attributed to the interaction
between CME1 and CME2. To reproduce the positive Bz component in the magnetic
ejecta of CME2, we had to initialise CME2 with an orientation determined at
0.1~au and consistent with the orientation interpreted at 1~au, instead of the
orientation observed during its eruption. EUHFORIA simulations suggest the
possibility of a significant rotation of CME2 in the low corona in order to
explain the in situ observations at 1~au. Coherent magnetic field rotations,
potentially geoeffective, can be formed in the sheath region as a result of
CME-CME interactions in the heliosphere even if the individual CMEs are not
geoeffective.
Solar coronal mass ejections (CMEs) can catch up and interact with preceding
CMEs and solar wind structures to undergo rotation and deflection during their
propagation. We aim to show how interactions undergone by a CME in the corona
and heliosphere can play a significant role in altering its geoeffectiveness
predicted at the time of its eruption. We consider a case study of two
successive CMEs launched from the active region NOAA 12158 in early September
2014. The second CME was predicted to be extensively geoeffective based on the
remote-sensing observations of the source region. However, in situ measurements
at 1~au recorded only a short-lasting weak negative Bz component followed by a
prolonged positive Bz component. The EUropean Heliosphere FORecasting
Information Asset (EUHFORIA) is used to perform a self-consistent 3D MHD
simulation of the two CMEs in the heliosphere. The initial conditions of the
CMEs are determined by combining observational insights near the Sun,
fine-tuned to match the in situ observations near 1~au, and additional
numerical experiments of each individual CME. By introducing CME1 before CME2
in the EUHFORIA simulation, we modelled the negative Bz component in the sheath
region ahead of CME2 whose formation can be attributed to the interaction
between CME1 and CME2. To reproduce the positive Bz component in the magnetic
ejecta of CME2, we had to initialise CME2 with an orientation determined at
0.1~au and consistent with the orientation interpreted at 1~au, instead of the
orientation observed during its eruption. EUHFORIA simulations suggest the
possibility of a significant rotation of CME2 in the low corona in order to
explain the in situ observations at 1~au. Coherent magnetic field rotations,
potentially geoeffective, can be formed in the sheath region as a result of
CME-CME interactions in the heliosphere even if the individual CMEs are not
geoeffective.
http://arxiv.org/icons/sfx.gif
